Method of producing vegetable adhesives



UNITED STATES PATENT oFFIcE.

ERNST STERN, or HANOVER, GERMANY.

v mETnoD or P oDocING VEGETABLE ADHESIVES. 7

No Drawing. I

Specification of Le'tters Patent. Patented Apr, 4,, 1922. Application filed March 24, 1915. Serial No. 16,772.

(GRANTED was: THE PRQVISIONS or THE ACT or mm s, 1921, 41 STAT. L., 1313.

To all'whom it may concern:

Be it known that I, Dr. ER sT STERN, a subjectof the King of Prussia residing at Hanover, inPrus's'ia, German Ilmpire, have invented a certain new and useful Method of Producing Vegetable Adhesives, of which the following is a specification.

My invention relates to a method of producing vegetable adhesives, and its object is 10 to reduce the costs of such production as well as to obtain products superior in quality.

In order to produce adhesives from starch orsubstances containing starch this latter is decomposed. with alkalis and more especially with caustic soda or potash. The products obtained after this manner have a great agglutinant power and are extensively used under the name of gluten or vegetable glue. Now in order to carry this process through and to obtain adhesives fit for. practical use it has proved necessary to employ certain rather big quantities of an alkali.

If this prescription is disregarded, the dc; composition of the material remains incomplete and the adhesive obtained will after some time be converted into a pastry sub stance absolutely unfit for use.

Now it has been ascertained that it is possible to reduce the quantity of alkali necessary for decomposing starch very considerably, if the decomposition is carried through under pressure. a

If starch-paste is heated in a closed vessel under pressure say to 125 to 130 degr. C.-, the

starch is temporarily liquefied, but no adhesive. is formed, as after-the solution obtained has cooled down, the starch which has been seeminglydissolved separates out again to the greater part and the entire solution coagulates into a elly-like mass.

If it is propose 'to convert the starch into sugar by aid of diastase (as in the manufacture of spirits), this coagulation is of no avail as the starch is, before coagulation can take place, decomposed further by the diastase,

On even'very small quantities of acid being added the result will always be a conare obtained which" are absolutely durable and possess extraordinary agglutinant qualities. Minute quantities of an alkali will produce this favorable efiect.

While the conversion of starch under or. dinary pressure, in order to produce adhesives, necessitates the addition of at least 2 per cent alkali, with increased pressure such as 5 atmospheres, or at least a pressure greater than 3 atmospheres and less than 15 atmospheres,only time per cent alkali, and even less, of the starch are required.

Consequently instead\ of caustic soda or potash a great number of salts having an alkaline reaction may be employed. Under ordinary pressure the conversion of starch into adhesives permanently fit for use by aid of carbonate, silicate or phosphateof tered. Weakerbases such as ammonia, further ammonium salts and organic bases may be employed also.

. Preferably .the process is carried out in an indifferent atmosphere (steam, nitrogen or the dike)- In some cases, however, an oxidizing atmosphere may prove useful;

The process may further be carried out with advantage'in the following way: the starch isfirst subjected to high pressure in a neutral solution; namely, the starch with an admixture. of Water but without alkali; wherebythe starch is converted into a soluble condition- After this conversion is soda .is impossible, ,whereas, if increased pressure is applied, no difiiculty 1's encouncompleted, very small quantities of hydroxyl In this modification of the process, the

starch is thus first dissolved and only then does the treatment "for obtaining the adhesive commence. This modified process has the advantage that no discolorations occur.

The adhesives obtained after this manner are distinguished by a very high agglutinant power and a high degree of fluidity.

Their' practically immaterial content of alkali renders them especially valuable as compared with a vegetable adhesives. I

The adhesives obtained after the process described are intended to be used in the first line asglue for wood. The principal qualities required for glue and which make great number of other the glue-adapted to glue wood togetherin the cold, are a superior spreading capacity in combination with a high agglutinaht power. Ingeneral these two qualities are not to be found in combination; if a coldglue 1 possesses the spreading capacity required for wood, it is generally lacking agglutinant power, and vice versa.- In order to overcome this difiiculty the process may be modified as follows:

It has been ascertained that the xanthogenates or xanthic'acid compounds of carbohydrates, and more especially of starch and cellulose, are apt to endow the coldglues with the superior spreading capacity required, without however depriving them of their high agglutinant power. If viewed 'in the light of colloidal chemistry, .the .xanthogenates may be said to form the sols which after having been spread upon the surfaces of woodto be glued, will be converted by the action of air into gels having a very high agglutinant power. The xantho genates of carbohydrates that are decom-v occurs only when the adhesive has been applied. This circumstance materially influences the durability of the wood-adhesive.

The process may further be carried out in the following manner: starch is subjected to a limited decomposing treatment and the starch thus partly decomposed is converted,

partly, into the xanthogenate by allowing carbon disulphide to act upon According to the degree of decomposltion of the starch and to the percentage of partly decomposed starch converted into xanthogen- 'ates (thiocarbonate) the spreading and gluing capacities of theproduct obtained will .be more or less pronounced.

To the starch-xanthogenate-glue a certain quantity of the corresponding cellulose compound may be added.

The compounds mentioned above are distinguished by their extraordinary capacity for jellification, this capacity being characteristic for an adhesive adapted to-be'used for gluing wood. Of course this capacity of forming jellies should be made use of in such away as to furnish a fluid glue permanently ready for use.

The following are examples of methods of carrying out the process.

Ewample I 200 kg. of starch is stirred thoroughly and finally disappears altogether.

with 200 kg. of water and brought by heating at 60 G. to the swollen condition. The swollen starch is then converted into its alkali compound by the addition, while the swollen starch is continually stirred, of 15 kg. of caustic soda dissolved in kg. of water. Thereupon carbon disulphide, for example 7.5- kg. thereof, while being kept quite cool, is added while the mass is sub- };cted continually to mechanical motion.

y observing a temperature of not above 25 (3., the formation of the thiocarbonate is completed in a few hours, and the progress of the reaction can be observed readily, inthat the odor of carbon disulphide less lens he product of the'process is a wood-glue of excellent qualities and durability.

The process may be modified by exposing the swollen starch, while in an autoclave provided with a stirring device, for about three hours tosteam pressure of' 5 atmospheres, for example. By this treatment, the starch gel passes over into a starch sol, and the conversion into the thiocarbonate results from the following treatment with alkali and carbon disulphide.

Example I].

200'kg. starch is mixed with 225 kg. of water into a mash and dissolved by the addition of 15 kg. of soda lye in 75 kg. of water. After solution has been effected, the temperature islowered to 40 C. and from 1 to 3 kg. ofa powerful diastatic malt extract, and in addition thereto 2 kg. of 3%, peroxide of 'hydrogen, are added thereto. Instead of this procedure, the decomposition may be brought about purely by oxidation, by adding from 2 to 4 kg. of 3% peroxide 105 of hydrogen. The temperature is gradually increased to 65 and the ingredients are kept at that temperature for one hour. Then they arewcooled down to from 20 to 25 and the redi ction into thiocarbonate is effected 11 by theaddition of from 8 to 10 kg. of disulphide of carbon.

- Ewample III.

2 kg. of cellulosic material is steeped in 6 kg. of 30% soda lye and the ingredients are left undisturbed for twenty-four hours. The soda lye is then squeezed off to such an extent that the weight of the alkaline-celluconverted into the alkaline compound, in the manner described in Example I. 20 50 kg. of the purified cellulose solution is applied to the prepared alkaline starch that' producing vegetable adhesives Which consists in heating carbohydrates of starch-like character under a pressure of from three; fifteen atmospheres with betweenone-half and one per cent of compounds having an a kaline reaction.

2. Method of prouucing vegetable adhesives which consists in heating carbohydrates of starch-like character under a pressure of from three to fifteen atmospheres with less than one per cent of compounds having an alkaline reaction. a

3. Methodaof producing vegetable adhesives which consists in partially decomposing a starch-like carbohydrate under the combined action of heat, pressure and minute quantities of an alkaline compound not exceeding one per cent of the, carbohydrate, and converting the partially decomposed carbohydrate lnto the corresponding xanthogenate.

4. Method of producing vegetable adhesives which consists in partially decomposing a starch-like carbohydrate under the comblned action of heat, pressure and minute quantities of an alkaline compound not exceeding one per cent of the carbohydrate, and treating the partially decomposed carbohydrate with carbon disulphide.

5. Asa new industrial-product, an ad-- consisting of a mixture of a starch-- hesive like carbohydrate and .the corresponding xanthogenate.

6. The process for the production of a Wood-glue which "consists in partially decomposing a carbohydrate and converting the new product into the corresponding xanthogenate.

7. Theprocess for the production of a wood-glue'which consists in mixing a starchlike carbohydrate and the corresponding xanthogenate in such mutually form a system of protecting colloids which normally prevent any chan from the sol condition to the gel condition.

8. As a new industrial product, an adhesive consisting of a mixture of a starchlike carbohydrate and the" corresponding xanthogenate in mutually form a system,of protecting colloids which normally prevent any change from thesol condition into the gel condition.

In testimony whereof I have signed my name to this specification. in the presence of two subscribing witnesses.

DR. ERNST sTERNo Witnesses:

HANS SCHULTZE, 1 HENRY REED.

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